Visible-Light-Sensitive SrCO3/AgI Hybrids for Tetracycline Degradation

The SrCO3/AgI photocatalysts were prepared via a co-precipitation method by using SrCO3 as a co-photocatalyst and AgI as a photo sensitizer.X-ray diffraction,field emission scanning electron microscope,X-ray photoelectron spectrometer,UV-vis diffuse reflectance spectroscopy and electrochemical impedance spectroscope were used to analyze the structure,micro-morphology,chemical compositions,optical properties and photo-generated carrier behaviors of the as-prepared samples,respectively.The photocatalytic degradation mechanism of the as-developed composites was also proposed.Analysis results show SrCO3,an insulator,can improve the photocatalytic performances and recyclability of AgI for degrading tetracycline under visible light.As the theoretical molar ratio of Sr(NO3)2 to AgNO3 increases,the degradation efficiency of the hybrids first increases and then descends.When the theoretical molar ratio of that is 1:1,it acquires the maximum of 66.6% within 8 min.This is higher than 32.0% of pure AgI and 34.0% of SrCO3.Moreover,after three times degradations it is 63.0%,which is higher than 13.6% of AgI.The improvement of the photocatalytic performance of the sample is attributed to the construction of hybrids.The main activated species in catalysis process are superoxide radicals.

In-situ Synthesis of SnO2 Quantum Dots/ZnS Nanosheets Heterojunction as a Visible-light-driven Photocatalyst for Degradation of Rhodamine B,Potassium Dichromate and Tetracycline

The SnO2 quantum dots(SnO2QDs)/ZnS nanosheets(ZnSNs)heterojunction was fabricated via an in-situ synthetic method at room temperature.Rhodamine B,potassium dichromate,and tetracycline were used to discuss the photocatalytic activities of the as-prepared samples under the visible light illumination.The photocatalytic mechanism of the as-prepared samples was also proposed.The experimental results indicate that the degradation efficiency of the as-prepared SnO2QDs/ZnSNs heterojunction first increases and then decreases with increasing the usage of ZnSNs.When the mass ratio of SnO2QDs to ZnSNs is 1:2 in 180 min,the as-prepared samples have the highest degradation efficiency of 89.1%for rhodamine B,97.7%for potassium dichromate,and 83.8%for tetracycline,which are much higher than 51.7%,26.8%,and 0.9%of pure SnO2QDs as well as 37.9%,87.1%,and 19.1%of pure ZnSNs,respectively.After it is repeatedly degraded for 3 times,it possesses the degradation efficiency of 62.5%for rhodamine B,which increases by 200.5%in comparison with 20.8%of the pure SnO2QDs.Moreover,the enhanced photocatalytic performances of the as-prepared hybrids are attributed to the formation of heterojunction between the SnO2QDs and ZnSNs.In addition,hydroxyl radicals and superoxide anion radicals play major roles during the photocatalytic degradation process,while holes play a minor role.